private static Type Create(DataReaderCache cache)
{
TypeBuilder tb = _mb.DefineType(
$"DynamicType_#{cache.GetColumnHash()}",
TypeAttributes.Public);
for (int fieldIndex = 0; fieldIndex < cache.Reader.FieldCount; fieldIndex++)
{
tb.DefineField(
cache.Reader.GetName(fieldIndex),
cache.Reader.GetFieldType(fieldIndex),
FieldAttributes.Public);
}
return(tb.CreateTypeInfo());
}
public static Type Get(DataReaderCache cache)
{
if (cache == null)
{
throw new ArgumentNullException(nameof(cache));
}
if (!_cache.TryGetValue(cache.GetColumnHash(), out Type value))
{
lock (_lock)
{
if (!_cache.TryGetValue(cache.GetColumnHash(), out value))
{
value = Create(cache);
_cache.Add(cache.GetColumnHash(), value);
}
}
}
return(value);
}
public static Func <IDataRecord, object> CreateMap(DataReaderCache cache)
{
if (cache == null)
{
throw new ArgumentNullException(nameof(cache));
}
if (!_maps.TryGetValue(cache.GetColumnHash(), out Func <IDataRecord, object> func))
{
lock (_lock)
{
if (!_maps.TryGetValue(cache.GetColumnHash(), out func))
{
func = Create(cache);
_maps.Add(cache.GetColumnHash(), func);
}
}
}
return(func);
}
public static Func <IDataRecord, T> Create(DataReaderCache cache)
{
if (cache == null)
{
throw new ArgumentNullException(nameof(cache));
}
if (!_cache.TryGetValue(cache.GetColumnHash(), out Func <IDataRecord, T> func))
{
lock (_lock)
{
if (!_cache.TryGetValue(cache.GetColumnHash(), out func))
{
func = CreateHelper(cache.Reader);
_cache.Add(cache.GetColumnHash(), func);
}
}
}
return(func);
}
private static Func <IDataRecord, object> Create(DataReaderCache cache)
{
Type instanceType = DynamicType.Get(cache);
var instance = Expression.Variable(instanceType, "instance");
var value = Expression.Variable(typeof(object), "value");
var record = Expression.Parameter(typeof(IDataRecord), "record");
var expressions = new List <Expression>
{
Expression.Assign(instance, Expression.New(instanceType))
};
for (var fieldIndex = 0; fieldIndex < cache.Reader.FieldCount; fieldIndex++)
{
var fieldName = cache.Reader.GetName(fieldIndex);
var fieldType = cache.Reader.GetFieldType(fieldIndex);
var getValueCall = Expression.Call(
record,
_getValueMethod,
Expression.Constant(fieldIndex));
var isNotDbNull = Expression.NotEqual(
value,
Expression.Constant(DBNull.Value, typeof(object)));
var memberExpression = Expression.MakeMemberAccess(
instance,
instanceType.GetField(fieldName));
var setCall = Expression.Assign(
memberExpression,
Expression.Convert(value, fieldType));
// Get the Value
expressions.Add(Expression.Assign(
value,
getValueCall));
// Only bother setting the value if is not dbnull,
// otherwise let the field stay at the default value
expressions.Add(Expression.IfThen(
isNotDbNull,
setCall));
}
var labelTarget = Expression.Label(typeof(object));
var labelExpression = Expression.Label(labelTarget, Expression.Default(typeof(object)));
expressions.Add(Expression.Return(
labelTarget,
Expression.Convert(instance, typeof(object))));
expressions.Add(labelExpression);
BlockExpression block = Expression.Block(
new[] { instance, value },
expressions);
var lambda = Expression.Lambda <Func <IDataRecord, object> >(
block,
record);
return(lambda.Compile());
}
